In conventional optical disks including a plurality of information layers, the positions in a thickness direction of the respective information layers are set in a way that allows optimum recording or reproduction with respect to the respective information layers (see a patent document 1, for example).    Patent Document 1: Japanese Patent Application Laid-Open NO. 2000-311346
However, the positions in a thickness direction of the respective information layers can be set arbitrarily in such optical disks as described above, and thus vary depending on the type of an optical disk. This increases the time necessary for detecting the positions of the respective information layers when accessing the layers by an optical disk device, resulting in longer access time.
Further, in an optical disk device that makes access by a converging spot, access is tried to information layers that cannot be accessed due to the positions thereof, which may cause a malfunction to occur.